Choppers are used to divide a continuous particle beam into spatially and temporally delimited pulses. A chopper is an element which comprises both regions that allow the particle beam to pass and regions that block the particle beam. As the chopper is moved through the particle beam, the open and blocked regions pass alternatingly through the particle beam, thereby modulating the particle beam.
Choppers configured as wheels, which are rotated through the particle beam, are known from DE 10 2004 002 326 A1. An essential aspect of the performance of such a chopper is the maximum frequency with which it can modulate the particle beam. This frequency is determined by the circumferential speed at the edge of the chopper wheel, which in turn is defined by the diameter and the rotational speed.
The aforementioned published prior art discloses that circumferential speeds of approximately 300 m/s are required for typical experiments. The published prior art discloses choppers which are designed as solid disks, as well as choppers segmented in a spoked manner in order to achieve such circumferential speeds.
The disadvantage is that the material of the chopper wheels is stressed to the limits of its mechanical strength, due to centrifugal forces. In addition, chopper wheels may oscillate. In practical applications, speed ranges in which the natural frequencies of the chopper wheels may be excited must be avoided. As a result, it is possible that the chopper cannot even be operated at a circumferential speed which it would be capable of, based on the mechanical strength thereof.